The present invention relates to methods for producing 3-dimensional wiring in encapsulated circuit boards for receiving surface mountable components and devices.
Initially circuit boards were designed to receive components such as semiconductors, resistors and capacitors by means of the conductor leads on the component which typically entered holes in the circuit board for soldering to terminals on the reverse side. More recently surface mountable components have been developed in which the mounting is effected by soldering terminal feet on the component to surface pads or lands on the surface of the board. The surface pads while representing a substantial improvement in circuit board technology are themselves difficult to fabricate. One method of forming such pads is disclosed in U.S. Pat. No. 3,688,396 in which a conductive metal layer of weldable material is etched to form a pattern of conductive lands or pads. In the process of fabrication, electrical conductors usually in the form of wires are joined to the inner or normally non-exposed surface of the pads. When the conductors are subsequently encapsulated in a molding material such as plastic there remain the exposed surfaces of the pads flush with the hardened encapsulating material to which surface-mountable components can be subsequently attached.
The object of the present invention is to provide a less complex and less expensive method of producing terminal pads on flat, single-sided, two-sided, or 3-dimensional circuit boards which will accommodate surface mount components and devices.